Hermetically sealed battery and method for manufacturing the same

Abstract

A sealed battery including: an electrode group 4 formed by winding or stacking a positive electrode plate 1 and a negative electrode plate 2 with a separator 3 interposed between the positive electrode plate 1 and the negative electrode plate 2 , and housed in a battery case 5 , an opening of the battery case 5 being sealed with a sealing plate, wherein a lead 11 extending from one of the electrode plates in the electrode group 4 is laser-welded to the sealing plate 10 , and a melting width of an end section 13 of a welded portion 9 between the lead 11 and the sealing plate 10 is smaller than a melting width of a center section of the welded portion 9.

The invention claimed is: 
     
       1. A sealed battery comprising:
 an electrode group formed by winding or stacking a positive electrode plate and a negative electrode plate with a separator interposed between the positive electrode plate and the negative electrode plate, and housed in a battery case, an opening of the battery case being sealed with a sealing plate, wherein 
 a lead extending from one of the electrode plates in the electrode group includes a welded portion linearly laser-welded to the sealing plate by continuously scanning a laser beam, 
 the laser beam has a spot diameter smaller than a thickness of the lead, 
 the linearly welded portion has, in its longitudinal direction, only one end section at which welding is started, and only one other end section at which welding is terminated, and 
 the only one other end section, of the welding portion, at which welding is terminated has a melting width in an extending direction of the lead narrower than a melting width in an extending direction of the lead of a center section of the welding portion, and 
 the melting width of the only one other end section at which welding is terminated of the linearly welded portion is substantially constant. 
 
     
     
       2. The sealed battery of  claim 1 , wherein the lead includes the welded portion formed by continuously scanning a laser beam having a spot diameter smaller than a thickness of the lead between its surface on which the welded portion is formed and a surface opposite thereto. 
     
     
       3. The sealed battery of  claim 1 , wherein the melting width of the center section of the linearly welded portion is substantially constant.